Though there isn't much in the game just yet, I still found myself enjoying bouncing off the walls and leaving all the particle trails behind me. Since I noticed in the description that the game was still a work in progress, it's possible you might intend to put in things like music and such later on already, which I think would add a lot! Sound effects in particular would enhance it a lot. I also noticed that while the "roof" and "ceiling" of the level had collision, the sides didn't. Because the rocket was also very slow to turn left and right, that meant that I would often have trouble controlling the rocket, and would end up flying off screen with no way of returning.
I would love to know when you've made updates, because this seems like this could be the foundation for a cool experience!